bird sitter, can I offer some advice? You put a poll out about who pens their ducks, and then you become offended when peeps give replies that you don't agree with. This makes no sense. BYC is a public forum, and anyone can post an opinion (in an appropriate way, of course, and no one has said anything offensive thus far in this thread.)
That said, I do a bit of both. Since I work full time, I am not home during the day, and I will not allow my ducks out when I'm not there to watch over them. I agree with others that it's my responsibility to provide good care & protect them when need be. On the other hand, I can't imagine that ANYONE can dispute that free range time is one of the best things you can do for a critter. For them to be able to pick & choose what to eat (research indicates they can actually "self medicate"; i.e., if they are lacking something in their diet, they'll seek out plants that are rich in it to supplement their systems), and I personally believe it's a sort of bonding/social thing for them to "run as a pack" as well.
However, ANY TIME you allow critters (expecially fowl) out of a safe enclosure, you're taking chances. It's a given, and you need to be prepared for the potential consequences. Some weigh it out and feel it's most definitely worth it, others do not. EITHER WAY, it's a personal choice, and neither is wrong.
I would also add that I do believe it's wrong to "smack down" anyone who does the opposite of what you believe is right. To say, "you have to pen them 24/7, as it's your responsibility to protect them" is a bit closed-minded in my book. "Protect them" may be, for some folks, allowing them to range. If that works for you, your flock is healthy and happy, then carry on! The opposite is true as well. There's absolutely nothing wrong with penning your birds if you are not in a situation where they will have protection when they're out free ranging. So, how about a bit more tolerance...from all? Just sayin'.